package com.ztom.top100;

/**
 * 二叉树的最近公共祖先
 * <p>
 * https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-tree/
 *
 * @author ZhangTao
 */
public class Code67LowestCommonAncestor {

    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode(int x) {
            val = x;
        }
    }

    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if (root == null || p == root || q == root) {
            return root;
        }
        TreeNode left = lowestCommonAncestor(root.left, p, q);
        TreeNode right = lowestCommonAncestor(root.right, p, q);
        if (left == null && right == null) {
            return null;
        } else if (left == null) {
            return right;
        } else if (right == null) {
            return left;
        }
        return root;
    }
}
